ARCHEAN

4.0 BILLION -2.5 BILLION: ARCHEAN

  • The Earth’s temperature 3 times hotter than today;
  • The Earth’s crust very thin;
  • Enormous volcanic and tectonic activity;
  • Protocontinents begin to form over hotspots;
  • Dense, hot atmosphere of CO², methane and ammonia;
  • Oceans hot, acidic and filled with dissolved metals;
  • First life appears as simple prokaryote bacteria;
  • Single-celled archaea extemophiles appear;
  • Cyanobacteria appear & begin forming stromatolites;
  • Cyanobacteria develop photosynthesis & begin pumping oxygen into the atmosphere.
Rodinia formed at c. 1.23 Ga by accretion and collision of fragments produced by breakup of an older supercontinent, and assembled by global-scale 2.1–1.82 Ga collisional events. Orogenic belts of 1.1 Ga age are highlighted in green.

Orogeny is an event that leads to a large structural deformation of the Earth’s lithosphere (crust and uppermost mantle) due to the interaction between tectonic plates.

  •  Earth was still about three times as hot as it is today;
  • Most of the Earth was covered with oceans;
  • Earth’s atmosphere was mainly carbon dioxide;
  • low oxygen levels;
  • Few small cratons formed by volcanoes;
  • Most of the rocks were igneous or metamorphic like granite or quartz;
  • Earliest sedimentary rocks like sandstone also formed in the oceans;
  • Earliest living cells formed in the oceans, evolved into simple prokaryote cells;
  • By three billion years ago, prokaryote cells evolved photosynthesis;
  • excreted (pooped out) oxygen;
  • Iron and sulfur rocks mixed with early oxygen atoms to make rusty red rocks and limestone;
  • Many large asteroids that hit the Earth during the Archaean Eon. 
Name Diameter (km) Age (megayears) Dating method Morphological type Notes
Hudson Bay Arc >450  <4,600  Arc rock age IMPROBABLE Multi ring basin? No impact metamorphism found